all of my pencil brushes are showing up as circles

Yes,

As far as I know (which isn't much), this is normal in Blender (GP). This is not like Krita, for instance, where Brush Cursors can have other shapes, depending on the Brush you are using.

I am really sorry, Owen,

I have absolutely no idea what you mean. The video doesn't help me understand. I do hope someone else can help you.

In your material you might have your stroke set to dots instead of line:

Hi Owen, i noticed in the video you are working in Solid Shading mode. Textures for brushes normally only show in material shading or rendered shading mode.

Textured brushes work best with dots/square materials for strokes, FYI. Setting it to line can have... interesting side effects haha